1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus. More particularly, the present invention relates to a developing cartridge for an electrophotographic image forming apparatus.
2. Description of the Related Art
As is well known in the art, an electrophotographic image forming apparatus is a printing apparatus, in which a toner is deposited on a photosensitive medium, where an electrostatic latent image is formed when a laser beam scans the photosensitive medium, thereby forming a toner image, and transferring the toner image to a paper being fed. Accordingly, a desired image is printed out. Since the electrophotographic image-forming apparatus has to be continuously fed with the toner, the electrophotographic image forming apparatus is usually provided with a separate toner storage means. The toner storage means is detachably mounted to the image forming apparatus body for replacement.
FIG. 1 is a schematic illustrating a conventional electrophotographic image forming apparatus. Referring to FIG. 1, the conventional electrophotographic image forming apparatus 100 comprises an exposure device 110, a developing cartridge 200, a transfer roller 120, a fixation device 130 and a paper-feeding device 140.
In the electrophotographic image forming apparatus 100 as constructed above, when a printing command is applied to the image forming apparatus 100, a laser beam in the exposure device 110 scans photosensitive drum 221 provided within the developing cartridge 200. Then, an electrostatic latent image is formed on the surface of the photosensitive drum 221, and the toner is deposited on the electrostatic latent image, thereby forming a toner image. When a paper is fed from the paper-feeding device, the toner image formed on the photosensitive drum 221 is transferred to the paper by the transfer roller 120. The toner image transferred to the paper is fixed on the paper as the paper passes through the fixation device 130.
In the above construction, the developing cartridge 200 has a predetermined lifespan, and is detachably mounted to the image forming apparatus body 101 for replacement.
As shown in FIG. 2, the conventional developing cartridge 200 is generally divided into a toner housing 210 and a photosensitive drum housing 220.
The toner housing 210 comprises a hopper housing 211 and a developing housing 212. The hopper housing 211 is provided with a toner storage chamber 211a, into which a toner is charged. A toner feeding chamber 212a is provided within the developing housing 212, and an agitator 213, a feeding roller 214 and a developing roller 215 are provided within the toner feeding chamber 212a. The toner feeding chamber 212a is opened to feed the toner to the photosensitive drum housing 220, in which the opened part is shielded by the developing roller 215, a restraint blade 216 and a shielding membrane 217. In addition, a photosensitive drum 221 and an electrification roller 222 for electrifying the photosensitive drum 221 are provided within the photosensitive drum housing 220.
The above-constructed conventional developing cartridge 200 is tested by examining an image produced using the developing cartridge 200, after the photosensitive drum housing 220 and the developing housing 212 are assembled, and a small amount of toner is fed thereto, while being manufactured.
If the developing cartridge 200 is in good order, a hopper housing 211 filled with toner is assembled to the developing housing 212. At that time, a shielding film 230 seals the toner storage chamber 211a of the hopper housing 211a to prevent leakage of the toner. If the toner storage chamber 211a communicates with the toner feeding chamber 212a, the pressure of toner moving to the opened part of the toner feeding chamber 211a increases. As a result, the toner may leak out due to vibration or external impact that can be caused during the transportation of the developing cartridge 200.
As can be appreciated from the above, in the conventional cartridge 200, the toner storage 211a and the toner feeding chamber 212a are partitioned by the shielding film, and therefore, the toner feeding chamber 212a is not used. Therefore, there is a limit in space for storing toner, which shortens a life span of the developing cartridge 200. In order to increase the toner-storing space, the size of the hopper housing 211 can be increased. However, this approach is not preferable since it will also increase the whole size of the image forming apparatus 100.
In addition, inconvenience will be caused when using the conventional cartridge 200 because a user has to detach and remove the shielding film 230 before mounting the cartridge to the image forming apparatus body 101. Furthermore, when the shielding film 230 is removed, the toner adhered to the shielding film 230 may be dispersed, thereby contaminating surroundings.